Yeah, Van Halen tuned down by one note as well.
Probably so that the singer could hit the high notes more easily, and it also loosens up the guitar strings so that bends are tapping are easier to play.
It used to really piss me off having to retune my guitar all the time whenever I learned a Van Halen tune :) Not to mention that you could never play the song live and have it sound exactly like the album. You couldn't afford to have a second guitar sitting around tuned down a whole step for just a couple of songs so you always played it in 440.